Influence of Limescale on Heating Elements Efficiency

A. Pezzin[1], M. Giansetti[1], A. Ferri[1]
[1]Politecnico di Torino, Torino, Italy
Published in 2013

Electric resistances are widely used as heating elements in domestic and industrial equipment; since process water contains calcium carbonate and calcium bicarbonate, limescale plays an important role on global efficiency of water-heating systems. Calcium carbonate has a very low thermal conductivity (2.2 W/(m*K)) and the carbonate deposit on the heating element causes a decrease of the overall heat transfer coefficient and consequently a reduction of the system efficiency. Assuming that our system is a simplified model of a washing machine heating system, considering a washing cycle at 60°C and assuming that every family in Italy has a washing machine, in the case of a 2mm limescale thickness the increase in energy consumption is about 75.8toe for every cycle.